Aqueous coating compositions of ethylene/acrylic acid copolymer and phenolic resin

ABSTRACT

Aqueous dispersions in which ethylene-carboxylic acid copolymers and a low molecular weight phenolic resin are combined to produce a material useful as an adhesive, insulator, primer or coating. Additives enhancing the properties of the composition are also disclosed.

United States Patent 1 1 11 1 3,843,576 Parkinson 1 1 Oct. 22, 1974 1 1AQUEOUS COATING COMPOSlTlONS OF ETHYLENE/ACRYLIC ACID COPOLYMER ANDPHENOLIC RESIN Inventor: Robert E. Parkinson, Monroeville Borough, Pa.

Assignee: United States Steel Corporation,

Pittsburgh, Pa.

Filed: Dec. 28, 1973 Appl. No.: 429,444

Related U.S. Application Data Continuation of Ser. No. 290,599, Sept.20, 1972, abandoned. which is a continuation-impart of Ser. No. 139,197,April 30, 1971, abandoned,

References Cited UNITED STATES PATENTS 2,902,458 9/1959 Teppema 260/2932,902,459 9/1959 Teppema 260/293 3,041,301 6/1962 Armour 260/2933,392,131 7/1968 Miles 260/848 3,438,931 4/1969 Mitchell 260/8483,644,262 2/1972 Stehle 260/296 R Primary Examiner-Morris LiebmanAssistant Examiner-P. R. Michl Attorney, Agent, or Firm-Ralph H.Dougherty [57] ABSTRACT Aqueous dispersions in which ethylene-carboxylicacid copolymers and a low molecular weight phenolic resin are combinedto produce a material useful as an adhesive, insulator, primer orcoating. Additives enhancing the properties of the composition are alsodisclosed.

6 Claims, No Drawings AQUEOUS COATING COMPOSITIONS OF ETIIYLENE/ACRYLICACID COPOLYMER AND PHENOLIC RESIN CROSS REFERENCE TO RELATED APPLICATIONThis is a continuation of application Ser. No. 250,599, filed Sept. 20,1972, now abandoned.

Application Ser. No. 290,599 is a continuation-inpart application of myapplication Ser. No. 139,197, filed Apr. 30, 1971 now abandoned.

BACKGROUND OF THE INVENTION Phenolic resins are well known for theirdurability, heat-resistance and water-resistance. These and otherfeatures make them desirable for use as adhesives and coatings forcellulosic materials or as coatings for metals. However, they arebrittle and do not perform well as adhesives for metals unless modifiedby substantial adhesion of resins that have better adhesion to metals,such as epoxies, or more flexible resins, such as nitrile or chloroprenerubber, or certain vinyl resins. Most phenolic resins are applied insolution in an organic solvent; however, some low molecular weightphenols are water soluble or dispersible.

Ethylene copolymers or interpolymers are flexible thermoplastic resinswhose properties generally resemble polyethylene. Certain of thesecopolymers, such as those of ethylene and a carboxylic acid such asacrylic acid have a superior ability of adhesion to various substrates.Such copolymers are often used as hot-melt coatings or adhesives, eitheralone or compounded with other thermoplastic resins, waxes, etc. Aunique property of certain of the ethylene-carboxylic acid copolymerswith high acid content is their ability to dissolve in aqueous alkali togive colloidal solutions by a reaction similar to saponification.

I have found that a solution or dispersion of ethylenecarboxylic acidcopolymers in a volatile alkali blended with solutions of phenolicresins can give a composition that may be applied and dried as acoating, which may be first reactivated (or fused to become tacky) andthen thermoset by heating, thus yielding a' strong, tough, flexiblematerial that has excellent adhesion to many substrates and is useful asa primer, adhesive, or coating. Modifications of this basic compositionhave been developed by addition of other materials such as other resins,fillers, pigments or dyes, solvents, surfactants, dispersants, orcross-linking agents, in order to improve such properties as stability,coatability and color.

One useful application of this composition is as a primer for use inconjunction with certain thermoplastic adhesive and coating materials,especially those based on ethylene copolymers, terpolymers, or ionomers,with and without modifiers such as coaltar pitch (US. Pat. No.3,361,692).

When bonded to fibrous or porous substrates, such as wood, paper,asbestos-cement, etc., these thermoplastic adhesive compositions are tooviscous, even at temperatures up to 500F (260C), to flow around thefibers or into pores to any considerable depth. While the adhesive mayadhere or bond to the superficial fibrous or porous surface, it does notpenetrate deeply. Such superficial surfaces are often weaker than thebulk of the substrate because they may be damaged by manufacturingoperations such as cutting or abradin'g. Thus,

bonds to such substrates may be relatively weak. Furthermore, bondsbetween metal and such fibrous or porous substrates are often subjectedto severe stresses when subjected to thermal or humidity changes becauseof great differences in expansion characteristics of the adherends.

US. Pat. No. 3,21 1,804 teaches a method for making an adhesive orcoating in which is added phenolic to olefin polymers not in anemulsion, nor in a water base dispersion, but merely blends the tworesins in order to improve their characteristics such as heatresistance, clarity, solvent resistance and adhesion. However, the flowindex is extremely low which indicates that the composition iscross-linked resulting in high viscosity and a loss of thermoplasticity.While my composition in the applied and cured condition has these samecharacteristics, it has the ability to flow readily, wet and adhere tothe surfaces to be joined, before cross-linking occurs. Thus, mycomposition can be easily applied to surfaces before curing.

Very few adhesives are capable of withstanding cycling tests such as theAmerican Plywood Associations soak-dry, hot-water-dry, orsoak-freeze-dry cycling tests with a metal overlay on plywood. To passsuch a test, it is necessary for an adhesive to be'very flexible andtough and its adhesion to both the metal and the fibrous or poroussubstrate must be very strong and moisture resistant.

A dilute solution of my composition, applied as a thin primer coating tothe porous substrates, penetrates and impregnates the surface fibers orpores and, when dried, binds and toughens the surface of the substrate.When the thermoplastic adhesive is applied with heat and pressuresufficient to cure the primeron the surface, the resultant adhesive bondis much stronger, more moisture-resistant-and more heat resistant thanthat without the primer.

A dilute solution of my composition is also advantageous when similarlyapplied to metal surfaces as a primer in conjunction with the abovementioned thermoplastic adhesive for use as adhesives or protectivecoatings. The low viscosity, low surface tension and soap-likeproperties of my composition make it possible for the primer to wet themetal surfaces, even when the surfaces are contaminated with a smallamount of oil or grease. The composition thus functions as a cleaner forthe metal. The dried primer coating reactivates and cures when heat andpressure are applied to bond the thermoplstic to the metal and gives abond between metal and the thermoplastic adhesive or coating that issuperior to that obtained without the primer under similar conditions.It is possible to obtain satisfactory bonds at lower temperatures andshorter time-at-temperature with such primed metal. The bonds withthermoplastic composition on the primed metal are stronger, more heatresistant and more durable on long time exposure to moisture than bondsmade without the primer. This improved performance with my primer isimportant when the thermoplastic composition is used either as anadhesive or as a protective coating on metal or other substrates forsevere applications such as a coating for the insides of culverts.

Adhesives are used for bonding metal faces to cores, such as plywood,paper or metal honeycomb, fiberboard, etc., as sandwich structures ormetal overlays for architectural, automotive, and other applications. Mycomposition is an excellent adhesive for such bonding. in suchapplications, it should be applied to the adherends as a moreconcentrated solution than that used as a primer, in order to build upan adequate thickness of glue line. No primer is necessary because thiscompound wets and adheres to the metal and penetrates the surface ofporous core materials. Afer drying, the metal and the core are assembledby applying heat and pressure to reactivate and cure the adhesive. Thebonds are strong both in shear and peel strength, and resistant tomoisture and heat.

This adhesive system has several advantages over competitive adhesivessuch as epoxies, rubberphenolics, or thermoplastics. it may bepreapplied and dried on the adherends from an aqueous solution (withoutfire hazard), the components can be assembled dry, and, when cured underheat and pressure, the adhesive is thermoset so that the pressure may bereleased and the panel handled while still hot without delamination (aswould occur with thermoplastic adhesives).

In addition to the use of my compositions as primers or adhesives, lhave also found that they may be used themselves as heat curing paints,enamels, or protective coatings. For such applications it isadvantageous to use more concentrated solutions (compared to primers) inorder to apply coatings of sufficient thickness to provide the requiredprotection. To the aqueous basic composition of ethylene copolymers andphenolic resins it may be desirable to add modifiers such as fillers,pigments, solvents, or other resins in order to obtain the desiredcoating characteristics. These coating compositions may be applied tometal or other substrates by spraying, roll-coating, or otherapplication processes as commonly used for other paints or enamels. Theyshould then be dried and baked to fully thermoset the resin composition.Such coatings have been found to be tough, flexible, abrasion resistant,and excellent protection from corrosion under severe moistureconditions.

Another specialized use of my composition is as a coating or core platefor use on steel sheets for electromagnetic cores such as those intransformers, generators, or motors. The cores of transformers and otherelectromagnetic structures are constructed of laminations to restrictthe flow of eddy currents and hereby reduce this component of theelectromagnetic core loss. For this to be successful, however, it isnecessary that each lamination be insulated from the others so that theeddy currents will not flow readily from one lamination to another. Insome cases, insulation, in addition to that from normal surface oxide,is supplied by coating the sheets or laminations with a thin coating ofvarnish or organic core plate," which has good electrical resistance andwhich is capable of maintaining this resistance under normal operatingtemperatures and pressures. When used in oil-immersed transformer cores,the core plate must not dissolve or react with the oil because theinsulating properties would be destroyed. The usual method of applyingthis coating is to pass the sheets or laminations through rolls coatedwith the composition, and then through a combination drying and bakingoven. The thickness and uniformity of the coating must be controlled toobtain adequate insulating properties. The coating should not be toothick, however, because this will, in effect, reduce the amount of steelin a core stack. Baking temperatures differ, depending on thecomposition and type of coating used. The organic varnishes require carein baking, since it is essential to volatilize off most of the vehicleand cure the resin to obtain a coating free from tackiness. Under-bakingresults in a soft, tacky or thermoplastic coating which will not havesatisfactory insulating properties under the pressure and temperatureconditions present in the core during service. Care also must be takento prevent over-baking because the varnish will become carbonized andthe insulation characteristics of the coating will be thereby impaired.

Presently used organic varnish core plate requires the use of flammableorganic solvents which are too hazardous for application under preferredplant conditions. There is a clear need in the art for a coating material which may be applied to the steel laminate but which is notflammable. This new material must also meet several other requirements,e.g., it must have good insulating properties (0.50 amperes maximum at300 psi and 150C ASTM A344-68), it should have an obvious color, it mustbe inert to oil, and it should be amenable to coating in dry thicknessesranging from about 0.15 mils to 0.03 mils (3.6 to 0.7 microns). Further,the coating should act as a lubricant for the die during punching of thecore forms.

My compositions can meet all the above requirements for a coating ofelectromagnetic steels, when applied as a thin, water-based coating,dried, and baked at sufficient temperature and time to thermoset thecoating as completely as possible without deterioration.

This core plate coating composition may also be used as an adhesive forbonding the sheets or lamillae of the electromagnetic cores by adifferent processing method. After applying the coating composition, itis dried at a temperature and time sufficient only to evaporate thevolatile materials but not enough to cure the coating. This uncuredcoating is tough and sufficiently adherent to withstand the fabricationand assembly of the core. After the core with the uncured coating isclamped together, it is baked to reactivate and cure the coating, thuscausing the sheets to adhere to one another. This process of adhesivebonding of electromagnetic cores may be of value in reducing the needfor mechanical fasteners to hold the core laminations together and forreducing the vibration and noise that occurs in unbonded cores becauseof magnetostriction.

The vibration damping properties of my adhesive compositions for bondinglaminates can be greatly improved by replacing about 20 to percent ofthe ethylene-acrylic acid copolymer with ethylene-vinyl acetatecopolymers or terpolymers or their acid which soften and improve theviscoelastic damping properties of the adhesive compound. Dispersions ofthese terpolymers and copolymers are available as Elvax D dispersionsfrom E. l. duPont de Nemours and Company. Bonded metal laminates withthese modified damping adhesive compositions have been found to be veryeffective in damping vibration and sound. They should be useful not onlyin reducing the noise and vibration of electromagnetic cores asmentioned above, but also for vibration and sound damping of metalcomponents of machines, appliances, furniture, 'etc.

Thus, among the objects of this invention are the following:

(1) To provide a thermosetting adhesive and coating composition that maybe applied from an aqueous dispersion.

(2) To provide a material for use as a primer on various substrates toimprove the bonds with certain thermoplastic adhesives and coatings.

(3) To provide an adhesive material suitable for bonding metal tovarious substrates such as metal, paper, wood, ceramics, etc.,especially for bonding laminates, or sandwich structures.

(4) To provide a material for use as a thermosetting coating, paint, orenamel for the protection of surfaces of metals and other substrates.

(5) To provide a material suitable for applying a thin insulating andlubricating coating or core plate to steel sheets for use in laminatedelectromagnetic cores.

(6) To provide an adhesive material with good viscoelastic propertiessuitable for bonding metal laminates to be used for vibration or sounddamping applications.

These and other objects will become apparent from the following detailedspecification.

DETAILED DESCRIPTION The copolymers of ethylene andethylenicallyunsaturated carboxylic acid suitable for use in mycomposition are those with preferably about 18 to about 24 percent ofacid by weight since these are more readily soluble or dispersible inalkali and they have better adhesion properties than those with loweracid content. Suitable acids copolymerized with ethylene to form thecopolymers are the ethylenically-unsaturated acids such as acrylic,methacrylic, crotonic, or isocrontonic acids. Preferred copolymers arederived from acrylic or methacrylic acid.

The acid groups of the copolymer react with hot solutions of aqueousalkali to form salts that disperse in water to form colloidal solutionsresembling soaps. Where the alkali is volatile, the colloidal solutionof the salt may be returned to the water insoluble acid form by drying,and heating to drive off the water and the volatile alkali. Aqueousammonium hydroxide is preferred, but any water soluble volatile alkalimay be used, including amines such as ethanolamine, diethylamine,morpholine or mixtures thereof. For making fluid solutions up to about24 percent resin solids, the resin is placed in an aqueous solutioncontaining at least a stoichiometric amount, and preferably from about10 to about percent in excess of the stoichiometric amount of volatilealkali. The mixture is heated and stirred in a closed vessel to atemperature usually of from about 90C to about 130C, and maintained atthis temperature while being stirred until the resin is dissolved. Usingthis method, fluid solutions containing up to about 24 percent resinsolids may be obtained in compositions which are useful for thin coatingsuch as primers or electromagnetic steel coatings. It is also possibleto obtain fluid solutions containing up to 30 or 40 percent resin solidsdepending on the molecular weight of the copolymer, by using less waterand less than a stoichiometric amount of ammonia. in this case thedispersion is partly a solution and partly a sol. These moreconcentrated solutions are useful for adhesives and thicker coatings.Ethylene-acrylic acid copolymer resins suitable for use in thecompositions of my invention are sold by Union Carbide Corporation underthe trade-names EAA-9300 and BAA-9500.

The total ethylene copolymer, terpolymer, and ionomer should comprisefrom about 25 to about 95 weight percent of the total resin solids,preferably from about 50 to about 86 weight percent.

Certain other dispersions of copolymers, terpolymers, or ionomers may besubstituted for all or part of the ethylene-acrylic acid copolymerammonium solutions in my composition in order to modify its properties.Such copolymer dispersions may contain ethylenevinyl acetate; terpolymerdispersions may contain ethy-' lene-vinyl acetate-carboxylic acids; andionomer dispersions may contain metallic salts of ethylenecarboxylicacids. Such dispersions are commonly made by proprietaryemulsion-polymerization methods and are often stabilized by surfactants.Typical dispersions of this type are commercially available as Elvax Dfrom E. I. duPont de Nemours Company. While 1 have obtained usefulcompositions substituting 100 percent of the above type of dispersionfor ethylene-acrylic acid dispersions, I have generally preferred tolimit the substitution to between 10 and 60 percent of the ethyleneresin solids depending on the application, since it appears that asubstantial proportion of the ethyleneacrylic acid copolymer solution isneeded to give better dispersion of the other components of mycomposition and better properties when applied as an adhesive orcoating.

One advantage of the mixed dispersions of ethyleneacrylic acidcopolymers with the above types of ethylene-copolymers, terpolymers andionomers, has been greatly increased stability of my compositions. lhave also found that the replacement of 40 to percent of theethylene-acrylic acid solids with these ethylenevinyl acetate copolymeror terpolymer modifies the properties of the dried and cured compoundssothat they have good viscoelastic damping properties and are useful asa sound or vibration damping adhesive layer between metal-laminates.Ethylene ionomer dispersion additions have not been found to contributeviscoelastic damping properties of the cured compound like the aboveethylene-vinyl acetate copolymers or terpolymers but they may stabilizemy dispersions and toughen the adhesive or coating.

The phenolic resins which may be used in my composition are preferablythose of the heat-reactable, watersoluble or dispersible, resol orA-stage type. These resins may be prepared by the alkaline catalyzedreaction of a phenol and formaldehyde. The reaction is stopped whenessentially no unreacted phenol is left and the product contacts asubstantial amount (more than 10 percent) of trimethylol phenol. Asuitable means of preparing resins of this type is disclosed in U.S.Pat. No. 2,834,755 dated May 13, 1958 to Higashi and Jarvi. Solutions ofresins of this type are produced by various companies under trade-namessuch as AROFENE 352 (Ashland Oil and Refining Co.), BAKELITE BRL- 1031(Union Carbide Corp.) or CASCOPHEN MB717-146 or SL699-l04A (BordenChemical Co.). Typical properties of these resin solutions are PhysicalForm: Aqueous solution While water soluble phenolic resins are generallypreferred because of ease of dispersing them in my composition, it isalso possible to use other heatreactable phenolic resins that aredissolved in alcohols orother solvents, by emulsifying the solution intothe ethylene-acrylic acid ammonium solutions. The phenolic resin maycomprise from about to about 75 weight percent of the total resinsolids, preferably from about 14 to about 50 weight percent. The greaterthe amount of phenolic resin, the greater is the high temperatureresistance of the composition.

The total resin solids in my composition varies according to final usebut generally should be between about 15 and 45 weight percent of theemulsion. Where superior wetting properties and a low solution viscosityare necessary, it is possible to have less resin solids than the statedgenerally useful minimum and still obtain most of the benefits of mycomposition.

Components other than the dispersions of copolymer and the phenolicresins are optional constituents added to improve such properties asstability, foam control, viscosity, and color. Suitable additioncomponents are coal tar fractions such as creosote, high boiling taroil, wax oil or pitch, surfactants, dispersants, solvents, crossJinkingagents, fillers, extenders, pigments, and foam control agents. The coaltar fraction may act as a suspension stabilizer, help preventdegradation of the ethylene copolymer by oxygen, provide moistureresistance, and have a plasticizing effect (especially the lower boilingfractions). The coil tar fraction may comprise from O to about 60 weightpercent of the total resin solids present.

Pigments or tillers, including inert oxides such as iron oxide ortitania or silicates such as clays or calcium silicate may be added tomy composition in finely divided form in amounts up to about 50 percentand preferably from about 5 to about 10 percent of the total solidsdepend on the final use of the composition. These components are addedto color, extend and improve the durability of the composition. Certainfillers such as calcium silicate may assist in catalyzing the cure ofthe composition;

In preparing the compositions of my invention, the first step is to forma dispersion of the ethylene and ethylenically unsaturated carboxylicacid copolymer. As described above, the ethylene copolymer resin isplaced in a pressure vessel with an aqueous solution of alkali to reactwith the carboxyl groups. When the resin used is the preferredethylene-acrylic acid copolymer and the alkali is the preferred aqueousammonium hydroxide, the mixture is heated to form about 90 to about 130Cuntil the resin dissolves, giving a soap-like aqueous solution ordispersion. The dispersion is transferred to a vessel having high-shearmixing apparatus. To this copolymer dispersion the desired quantity ofphenolic resin, along with other resin dispersions, fillers, pigments,is added with vigorous stirring. The pH of the phenolic resin solutionshall be adjusted over pH 8 by the addition of ammonia, amines or otheralkali.

Small amounts of surfactants, defoamers and solvents may be added forease in preparing my compositions.

surfactants such-as acetylenic glycols may be added to the copolymeremulsion.

The composition of my invention is then applied to a substrate in anyconventional manner such as dipping, spraying, rolling, etc. and dried.in applications which do not require maximum adhesion obtainable usingthe composition of my invention, the cleaning of the substrate may bereduced or eliminated prior to coating, since the coating itself is agood detergent. Among the suitable substrates are metals includingcarbon, stainless, galvanized, aluminum coated or silicon electricalsteels, wood, fiber board, paper, galvanized steel, etc.

The following examples illustrate the results obtained when specificcoating compositions are applied to several types of substrates. Theseexperiments are to be understood as being merely illustrative and in noway limiting.

EXAMPLE l The simplest composition of my invention was prepared bymixing the phenolic resin solution into the ammonium solution of theethylene-acrylic acid co- Thus, pyridine, xylene, diacetone alcohol,etc. may be polymer. As an example, twenty-seven parts of ARO- FENE 352(phenolic resin) is slowly added to parts of a 20 percent solidsammonium solution of EAA 9300 with vigorous stirring, to giveapproximately equal parts of phenolic resin and copolymer resin solids.The addition of ten to thirty parts of ethanol or 2-propanol reducesfoaming and improves wetting and stability of the solution somewhat butis not necessary for the performance 'of the compound. The resultingmixture is a very fluid, light brown, milky colloidal solution. It haslow surface tension and a tendency to foam. The shelf life of thismixture at 24C is limited to about 2 to 15 days after which the solutionbecomes green in color and a brown precipitate of phenolic resinsettles. When refrigerated at about 8C, the composition is stable forlonger than six months.

Coatings of these compositions, dried and heated at about 300F for 20minutes or 450F for 1 minute the thermoset as indicated by loss of tackand increased hardness at elevated temperatures. When applied to metals,such as carbon steel, galvanized steel or stainless steel, the solutionwets the surface well, and the cured coating is very adherent, tough,and heat and moisture resistant. When used as a primer (usually as amore dilute solution) applied to metals, wood, or paper, these compoundsimprove the strength and durability of bonds of certain otherthermoplastic adhesives, especially those containing ethylenecopolymers, such as USS NEXUS P-l00l or P- 1003, and duPonts Surlyn A.

EXAMPLE 2 Coal tar pitch is added to the ethylene-acrylic acidphenolicdispersions as extenders to improve durability, moisture resistance, andadhesive properties of the compounds. Blends with coal tar pitch aremore stable at room temperatures than the ethylene copolymerphenolicdispersions without pitch. A typical formulation (SX 900l-6870-50A) isas follows:

100 parts (by weight) ethylene-acrylic acid copolymer (EAA 9300)dissolved in aqueous ammonia (20 percent solids) parts phenolic resin(about 70-75 percent solids) (AROFENE 352) parts coal tar pitch (70Cfiber grade) parts ethanol or 2-propanol (to assist wetting of substrateand drying of coating) 10 parts xylene (to dissolve pitch) 5 partspyridine (to aid in dissolving and dispersing pitch) 1 part l-octanol(antifoam) This compound may be blended by milling in a ballmill or bydissolving the pitch in the xylene and pyridine and mixing it into theother components with a high-shear mixer until the pitch is colloidallydispersed.

When the pitch is adequately dispersed, this compound has a shelf-lifeof at least several months at a room temperature of about C.

EXAMPLE 3 The composition of Example 2 is coated on steel as a primerfor an adhesive prepared according to Example l of US. Pat. No.3,361,692. Without the primer the adhesive has a peel strength of 19 to37 lbs per inch; with the primer, the peel strength is 69 to 77 lbs perinch (ASTM Test D 903).

EXAMPLE 4 The composition of Example 2 is used as a primer forsteel-to-plywood bonds using the adhesive of Example 3. Using 0.018 inchcarbon steel, the peel strength increases from 32 to 50 lbs per inch to90 to 130 lbs per inch.

EXAMPLE 5 The heat resistance of the bond produced in Example 3 istested. A lap adhesive joint is made with and without the primer andheated in an oven. Without the primer the bond fails at 77C. With theprimer the bond fails at 90C. Thus, heat resistance of the bond whenprimer is used is found to be improved.

EXAMPLE 6 Bonds of galvanized steel with duPonts Surlyn A adhesive filmare greatly enhanced by the application of the composition of Example 2as a primer. The primer is applied as a thin coat to the galvanizedsteel surfaces and dried two to ten minutes at 150C. Then the Surlyn A1555 film is placed between the primed surfaces under pressure and theassembly heated to about 200C. Lap shear tests at room temperature onthe bonds with the primer give cohesive breaks at about 2,600 psi;without primer, the breaks are partially adhesive and bonds fail at from900 to 1,400 psi (ASTM D1002).

EXAMPLE 7 A composition is made similar to that in Example 2 but withhigh-boiling coal tar oil (95 percent boiling above 355C) substitutedfor the 70C fiber grade pitch fraction of coal tar. This composition iseasier to produce because the tar oil is more readily colloidallydispersed than the pitch, using simple high-shear mixers. The tar oilhas the same stabilizing effect on the copolymer-phenolic as the pitchaddition, and there is no significant settling during storage at roomtemperature for several months. Performance is comparable to Example 2formulation.

EXAMPLE 8 When used as an adhesive or coating by itself (rather than asa primer for another adhesive or coating), it is often desirable to havea higher solids content in the dispersion in order to obtain thickercoatings. The formula of such an adhesive is as follows in parts byweight:

Ethylene-acrylic acid copolymer (30% ammoniacal dispersion of EAA 9300)Phenolic resin (BRL-l03l Z-Propanol High-boiling tar oil 995% boilingabove 355C) Xylene Morpholine (optional, to adjust viscosity) Thehigh-boiling tar oil is combined with the xylene and morpholine, mixedwith the phenolic and added to the copolymer dispersion to which the2-propanol has previously been added.

This compound is used for bonding steel wire to fiber pads. The wire isdipped in the dispersion, dried, and then heated to about 200C whilebeing pressed against the fiber. This compound gives a sufficientthickness of coating on the wire and during the heating it first becomestacky and soft so that it penetrates and adheres to the fiber and thenthermosets, becoming rigid and tack-free at 200C.

EXAMPLE 9 It is desirable to add substantial amounts of fillers and/orpigments to these compounds to improve their properties againstmoisture, heat, wear, weathering, and other exposure conditions; tocolor the coatings; to reduce their cost; to thicken the dispersions toobtain thicker coatings and to control penetration into the substrates;or to reduce their thermal expansion coefficients to more nearly matchthat of the substrates. An example of such filled composition is asfollows:

Ethylene-acrylic acid copolymer (per Example I) i 300 ml Phenolic resin(BRL-l03l) 14 ml High-boiling tar-oil 14 ml Morpholine 2 ml 2-propanoll0 ml Xylene 7 ml Calcium silicate 30 g Iron oxide (precipitator dust)30 g Magnesium Montmorillonite 3 g Lignosulfonate 1.2 g

These ingredients are readily blended in a high-speed mixer. The2-propanol is pre-mixed with the phenolic resin and the xylene with thetar oil to assist in dispersion. This compound, applied to metal, dried,and cured at about 200C for 5 minutes, forms a tough, adherent coating.It can also be applied to metal and plywood, dried, and partially curedat 200C for about 3 minutes with the faces open to give a tough coating.When these coated surfaces are assembled and placed in a hot platenpress at about 200C for 15 to 60 seconds, the compound reactivates andthen cures, forming a strong adhesive bond with good moisture and heatresistance. When the metal is pulled from the plywood, the failure isdeep in the wood.

EXAMPLE EXAMPLE 1 1 An adhesive composition suitable for bonding metalfaced paper honeycomb sandwich panels is shown designated as No. 2adhesive in Table I. Table III compares the flexure strength of suchbonded sandwiches with sandwiches using adhesives known to the art. Theadhesive dispersion is applied to the honeycomb cell edges byroll-coating or dipping and then dried. These coated paper cores may bestored for many months before assembly. The metal facing sheets may beprimed with a similar but more dilute composition, but this is notessential. The heated sandwich is heated to 350to 365F for 1 minute ormore under contact pressure to cure the composition.

EXAMPLE l2 A composition of my invention suitable for use as a coatingor core plate for steel sheets for electromagrietic cores is preparedaccording to the formula in Table W. The compound consists essentiallyof a mixture of ethylene acrylic acid copolymer ammonium soiution andaqueous phenolic resin solution with minor additions such as alcohols,monoethanol amine and surfactant to improve coating characteristics andstability of the mixture, and phosphate to catalyze the cure. Thecomposition is prepared by pre-mixing the two parts as indicated inTable IV and then blending Part A into Part B with a high-shear mixer.

The composition is applied to coils of steel for electromagnetic coreapplications by roll-coating, dried and cured by passing through an ovenso that it is exposed to a temperature between about 370C and 425C forabout 30 seconds. The dry coating thicknesses are about 1 to 3 micronsthick and are dark brown in color. The Franklin insulation values (ASTMA344-68) are good (less than 0.50 amperes at 300 psi and l50C). insubsequent fabrication of the coated sheets into electromagnetic cores,the die-life is approximately doubled, indicating better lubricatingproperties than that of conventional varnish coating.

EXAMPLE 13 The procedure of Example I2 is followed to prepare a likecomposition set forth in Table IV differing principally from thecomposition of Example 12 in that an ethylene-methacrylic acid ionomerdispersion or an ethylene-vinyl acetate dispersion is substituted for aportion of the ethylene-acrylic acid solution. Minor additions such aslignosulfonate and bentonite clay dispersants and diacetone acrylamidecrosslinking agent assist in curing the composition.

EXAMPLE 14 This composition is more stable for long time storage thanthat of Example l2, especially when the concentration exceeds 30 percentsolids.

Elvax D l 1 l2 copolymer dispersion is substituted for the Elvax D 1249ionomer dispersion of Example 13 in the same amount and mixed as inExample [2. The resulting compound is applied to steel sheet and driedonly (not cured). Laminates are made by pressing two coated sheetstogether at about 200C and psi for 1 hour to reactivate and cure theadhesive compound and bond the sheets together. The sample is tested forsound damping quality by the vibrating reed test. Reverberation timeranges from about one second at room temperature to about 0.08 second atfrom C to l50C. This compares to about 4 to 5 seconds for solid steel ofthe same thickness as the laminate.

EXAMPLE 15 Three compositions are used as primers for an adhesiveprepared according to Example 1 of U.S. Pat. No. 3,361,692 and theresults compared. Primer No. l is the ethylene-acrylic acid copolymerdissolved in suff cient ammonium hydroxide to give a dispersion having20 percent solids. Primer No. 2 is the same copolymer blended with aphenolic resin. Primer No. 3 is the same copolymer blended with aphenolic resin and coal-tar pitch. The compositions are listed in TableV. The primers were applied to the plywood and dried at C for 2 to 10minutes. The adhesive film was first laminated tothe steel sheet byheating to about 200C. The coated sheet and the primed surface of theplywood are then reheated and assembled in a roller press. Table VIshows the results of peel tests on these steelto-plywood bonds andindicates that all three primers increase the bond strength, Primer No;3 being outstanding.

EXAMPLE 16 A sandwiched structure with a paper honeycomb core is bondedusing an adhesive as disclosed in Example l of U.S. Pat. No. 3,361,692and the ethylene copolymer phenolic coal-tar pitch composition ofExample 3. The results indicate that the primed structures are strongerboth in flexure and peel strength than commonly used high-qualitycontact adhesives and equal in flexure but superior in peel strengthcompared to epoxy adhesives. Procedure for making these honeycomb andsandwiched structures is to: (1) Apply the primer to the cell edges ofthe paper honeycomb and dry it; (2) Assemble the panels with the looseadhesive film interleaved between the core and each of the steel faces;and (3) Hot press the assembly at about 200C for 0.5 to 10 minutes atcontact pressure to cure the composition.

EXAMPLE I! Steel facing is bonded to maple lumber using an adhesive asdisclosed in Example 1 of U.S. Pat. No. 3,361 ,692. The unprimed jointhas a peel strength of 28 33 ppi. The peel strength, when primed with aprimer having the composition of Primer No. 3 in Table V, is 48 57 ppi.

Table l No. 1 Adhesive Designed for Components Metal to PlywoodEthylene-acrylic acid No. 2 Adhesive Designed for Metal to PaperHoneycomb polymer using 30% solids 200 ml 200 ml ammoniacal emulsionPhenolic resin solution (per Example 1) 30 ml 20 ml High-biling tar-oil(coal-tar) 3.5 ml 3.5 ml Xylene 5 ml 5 ml Calcium silicate 5 grams 5grams Filler (iron oxide) grams Miscellaneous additives to adjustviscosity dispersion foaming or adhesion 0.8 grams 3.0 grams Table IITable III Average Joint Strength of 20 Flexure Strength of Steel-FacedMetal-to-Plywood Bonds Paper-Honeycomb Sandwiches (Adhesive No. 1)Bonded with Various Adhesives Tensile Shear Strength 875 psi ASTM C-393l inch square lap of 0.062-inch thick steel to fir plywood. Tested dryat room temperature) Peel Tests (ASTM D903, with 0.0l8-inch thick steelto fir plywood) Tested dry at room temperature Tested dry at 250F Testedat l20F after exposure at 150F, l00% relative humidity for:

1 day 3 days 7 days Tested at approximately 100F after exposure at thattemperature for:

8 hours 24 hours l00% wood failure) 25 Flexural Load to Failure Poundsper inch width Approximately 75 to 80 percent wood failure"Approximately 50 to 60 percent wood failure 39 Ppi* Epoxy Adhesive 25PP' USS NEXUS ssooa 15o Thermoplastic Film Adhesive pp USS NEXUS Pl003(alone) 85 37 ppi* 25 ppi" 35 USS NEXUS P1003 with primers PX 2001 or SX9001 172 pp Adhesive No. 2 (Table l) I72 25 pp] Samples were 3 inch by14 inch by 1 inch thick tested with lZ-inch span,

40 quartcr-pointloadingi Honeycomb cores were Union Camp Corpv (t 80)'A)longitudinal Carbon steel faces were 0.047 inch thick Table IV SampleCore-Plate Formula Parts b Wei ht xamp e 1 Example 13 Part Aethylene-acrylic acid copolymer (22% solids ammonium solution 300 190.0

of EAA 9500) ethylene-methacrylic acid ionomer dispersion (42% solids)180.0

Elvax D 1249 (du Pont) acetylenic glycol surfactant and anti-foam 0.60.4 lignosulfonate 2.0 bentonite clay 3.6 diacetone acrylamide(crosslinking agent) 12.0 amide-ammonium phosphate (30% aqueoussolution) 7.5 ammonium phosphate, dibasic (33% aqueous solution) 7.5

Part B phenolic resin solution AROFENE 352 60.0 350 (code 595-090)(Ashland Chemical Co.)

l-butanol 7.0 4.5 furfuryl alcohol 2.5 monoethanolamine 5.0 3.5 ethanol8.0

Total 388.1 4410 Estimated total solids 32.6% 36.7%

Table V Primer Compositions Primer No. l 2 3 Ammonium solution ofethylene-acrylic acid copolymer (20% solids) 100% 66.7% 50% (perExample 1) (by vol) (by vol) (by vol) Phenolic resin (per Example I) 9%7.8%

Coal-tar pitch 70C Fiber grade) 0 0 5.0%

Ammonium hydroxide (excess) 0 2.25% 0 Ethanol 0 10.6% 0

2-P'ropanol O 0 100% Xylene 0 0 5.0%

Pyridine O 0 2.5%

l-Octanol 0 0 0.5%

Water 0 ll.2% 20.25%

Percent Solids 20% 20% 20% Table VI Peel Strengths of Steel-to-PlywoodBonds Primer Peel Strength Adhesive on Plywood lb/inch Failure USP3,361,692

Example 1 None 32-50 In superficial wood fibers USP 3,36] .692

Example I No. l 46-57 Somewhat deeper in wood USP 3,361,692

Example I No. 2 45-61 Deeper in wood and some cohesive USP 3,361,692

Example 1 No. 3 90-l30 Cohesive in adhesive film Tested as manual I80degree peel of inch wide, 26 gage carbon steel strips bonded to exteriorgrade fir plywood.

I claim: I. A composition useful as a coating or adhesive consistingessentially of an aqueous dispersion of:

a. from about 25 to about 95 weight percent of resin solids of acopolymer of ethylene and acrylic acid, wherein the acrylic acidconstitutes about 18% to 24% of the copolymer; said copolymer beingdissolved in aqueous ammonium hydroxide to form an ammonium salt orionomer solution or dispersion;

b. from about 5 to about weight percent of resin solids of a waterdispersible, heat reactable, resol, A-stage type phenolic resin,essentially free of unreacted phenol and containing a substantial amountof trimethylolphenol.

2. A composition as in claim 1 including an ethylenemethacrylic acidionomer, said ionomer containing at least 75 percent ethylene andconstituting not more than 60 percent of the total resin solids.

3. A composition as in claim 1 including an ethylenevinylacetatecopolymer or ethylenevinylacetateethylenically unsaturated carboxylicacid terpolymer containing at least 20 percent ethylene and constitutingnot more than 75 percent of the total resin solids.

4. A composition .for the application as coatings or adhesivesconsisting of an aqueous dispersion of:

a. from about 25 to about weight percent of resin solids of a copolymerof ethylene and an acid selected from the group comprising acrylic andr'nethacrylic acids, wherein the acid constitutes about 18 to 24 percentof the copolymer; said copolymer being dissolved in aqueous solution ofa water soluble volatile alkali to form an alkali salt or ionomersolution or dispersion;

b. from about 5 to about 75 weight percent of resin solids of a waterdispersible, heat reactable, resol, A-stage type phenolic resin,essentially free of unreacted .phenol and containing a substantialamount of trimethylolphenol.

5. A composition as in claim 4 including an ethylenernethacrylic acidionomer, said ionomer containing at least 75 percent ethylene andconstituting not more than 60 percent of the total resin solids.

6. A composition as in claim 4 including an ethylenevinylacetatecopolymer or. ethylenevinylacetateethylenically unsaturated carboxylicacid terpolymer containing at least. 20 percent ethylene andconstituting not more than 75 percent of the total resin solids.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION October 22, 1974Patent No. 378 576 Dated -'Robert E. Parkinson Inventor(s) It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 6, line 67, delete entire line and insert Specific Gravity at v25 C/Z5 C. 1 235 1 255 Column 10, line 16, "995%" should read (953Column 12, under EXAMPLE '14, cancel the first paragraph, lines 3-5, andinsert same in Column 11, under EXAMPLE 13, as the last paragraph.

Signed: and sealed this 21st day of January 1975.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents FORM po-1oso (10-69) l USCOMM-DC scene-pea U.5. GOVERNMENTPRINTING OFFICE: 6 9, 93 o

1. A COMPOSITION USEFUL AS A COATING OR ADHESIVE CONSISTING ESSENTIALLYOF AN AQUEOUS DISPERSION OF: A. FROM ABOUT 25 TO ABOUT 95 WEIGHT PERCENTOF RESIN SOLIDS OF COPOLYMER OF ETHYLENE AND ACRYLIC ACID, WHEREIN THEACRYLIC ACID CONSTITUTES ABOUT 18% OF 24% OF THE COPOLYMER, SAIDCOPOLYMER BEING DISSOLVED IN AQUEOUS AMMONIUM HYDRXIDE TO FORM ANAMMONIUM SALT OR IONOMER SOLUTION OR DISPERSION. B. FROM ABOUT 5 TOABOUT 75 WEIGHT PERCENT OF RESIN SOLIDS OF A WATER DSPERSIBLE HEATREACTABLE, RESOL, A-STAGE TYPE PHENOLIC RESIN, ESSENTIALLY FREE OFUNREACTED PHENOL AND CONTAINING A SUBSTANITAL AMOUNT OFTRIMETHYLOLPHENOL.
 2. A composition as in claim 1 including anethylene-methacrylic acid ionomer, said ionomer containing at least 75percent ethylene and constituting not more than 60 percent of the totalresin solids.
 3. A composition as in claim 1 including anethylene-vinylacetate copolymer or ethylene-vinylacetate-ethylenicallyunsaturated carboxylic acid terpolymer containing at least 20 percentethylene and constituting not more than 75 percent of the total resinsolids.
 4. A composition for the application as coatings or adhesivesconsisting of an aqueous dispersion of: a. from about 25 to about 95weight percent of resin solids of a copolymer of ethylene and an acidselected from the group comprising acrylic and methacrylic acids,wherein the acid constitutes about 18 to 24 percent of the copolymer;said copolymer being dissolved in aqueous solution of a water solublevolatile alkali to form an alkali salt or ionomer solution ordispersion; b. from about 5 to about 75 weight percent of resin solidsof a water dispersible, heat reactable, resol, A-stage type phenolicresin, essentially free of unreacted phenol and containing a substantialamount of trimethylolphenol.
 5. A composition as in claIm 4 including anethylene-methacrylic acid ionomer, said ionomer containing at least 75percent ethylene and constituting not more than 60 percent of the totalresin solids.
 6. A composition as in claim 4 including anethylene-vinylacetate copolymer or ethylene-vinylacetate-ethylenicallyunsaturated carboxylic acid terpolymer containing at least 20 percentethylene and constituting not more than 75 percent of the total resinsolids.